1. Field of the Invention
The present invention relates to a semiconductor device, a method for manufacturing the same, and a thin film capacitor, and in particular, relates to a constitution of a semiconductor device integrated with a thin film capacitor which functions as a decoupling capacitor.
2. Description of the Related Art
When a load is applied very rapidly to a semiconductor integrated circuit device (hereinafter, called an LSI), a voltage drop is observed due to a parasitic resistance and a parasitic inductance present between the power source and ground wirings of the LSI. The voltage drop becomes larger when the parasitic resistance and the parasitic inductance increases, and when the fluctuation time of the load current becomes shorter. The operational frequency has been increased recently from several hundreds of MHz to a level on the order of GHz, and the rising time of the clock has become very short, so that voltage drops have become larger, which causes malfunction of the LSI. In order to reduce such a voltage drop for such reasons, an effective measure is to dispose a capacitor between the power source line of the LSI and the ground wirings of the LSI in parallel. This capacitor disposed in parallel is generally called a decoupling capacitor. When the LSI is temporarily subjected to a voltage drop, the charge accumulated on both electrodes of the capacitor is instantaneously discharged so that the temporal drop of the source voltage can be compensated.
When an ideal state is assumed in which the equivalent series inductance and the equivalent series resistance of the decoupling capacitor is zero, it is possible to discharge the charge instantaneously, and to suppress the voltage fluctuation to zero. In practice, however, since the capacitor has a certain amount of equivalent series inductance and equivalent series resistance, an LC resonance is generated and the capacitor does not work above the resonant frequency. Therefore, as the operational frequency of the LSI increases, it is necessary to reduce the equivalent series inductance of the decoupling capacitor and to shorten the distance between the LSI and the capacitor.
Conventionally, a discrete multilayer ceramic capacitor has been used, because it has a comparatively small equivalent series inductance at a high frequency range. The discrete multilayer ceramic capacitor has a features that its equivalent series resistance and the equivalent series inductance are small when compared with an electrolytic capacitor and in practice, the equivalent series inductance can be reduced to a level of 0.4 nH for a capacitor with a capacitance of 0.01 xcexcF. Therefore, the voltage drop has been conventionally prevented by disposing a number of multilayer ceramic capacitor around the LSI which performs a high speed operation. FIG. 13 shows a conventional example, in which a number of multilayer ceramic capacitors 13 functioning as decoupling capacitors are mounted around the LSI chip 12 mounted on a printed circuit board 11.
Conventional examples, in which decoupling capacitors are disposed at the nearest positions to the LSI, are disclosed in Japanese Unexamined Patent Application, First Publications No. Hei 7-183470 and No. Hei 7-183459. In these conventional examples, the decoupling capacitors are adhered to the upper surface of the LSI using a conductive adhesive.
Accordingly, manufactures of the conventional semiconductor integrated circuits used to provide a plurality of types of LSIs, the operational frequency of each of which was guaranteed, for the convenience of customers"" selection, or manufacturers often manufactured LSIs in accordance with customer designs.
When the performance of a capacitor is considered, the resonant frequency of the above-described discrete multilayer ceramic capacitor is at a level of approximately 80 MHz, so that the multilayer ceramic capacitor cannot compensate for the voltage drop of the LSIs which are operated at several hundreds of MHz or on the order of GHz. Furthermore, the decoupling capacitors arranged shown in FIG. 13 occupy a considerable area of the printed circuit board, so that such arrangement is disadvantageous in reducing the size of the electronic devices.
The method of adhering a capacitor on the surface of an LSI as disclosed in Japanese Unexamined Patent Application, First Publications No. Hei 7-183470 and No. Hei 7-183459 cannot cope with operations in a higher frequency range of more than several hundreds of MHz because of the resistance of the adhesive and contact resistance of the capacitor with the LSI, and because of the presence of an inductance component resulting from the shape of the adhesive.
The fact that the equivalent series inductance of the decoupling capacitor can be decreased by decreasing the thickness of the dielectrics constituting the capacitor has been known. Although the thickness of the dielectric layers in the discrete multilayer ceramic capacitors are generally on the order of a micronmeter, the thickness of the dielectric layers in the thin film capacitor used inside of the LSI is on the order of a nanometer, so that the equivalent series inductance is quite small and the decoupling capacitor is operable in the GHz frequency range.
In particular, when a dielectric film is used such as (Ba, Sr)TiO3 having a higher dielectric constant than SrTiO3 which has the high dielectric constant of 300 at room temperature, it is possible to increase the charge stored per a unit area to more than several tens of times than the SiO2 or Si3N4. This is because the dielectric constants of the SrTiO2 or (Ba, Sr)TiO3 are 300 to 500 or more, while the dielectric constants of SiO2 and Si3N4 are 3.9 and 7.
An example of forming a decoupling capacitor on an aluminum nitride using a SrTiO3 film deposited by sputtering as a dielectric material is disclosed in Japanese Unexamined Patent Application, First Publication No. Hei 8-97360. However, in this example, the decoupling capacitor was formed on the printed circuit board for mounting a multi-chip module, so that the deposition temperature for depositing SrTiO3 is limited. In general, it is known that the dielectric constant becomes high when this type of dielectric material is formed at high temperature. Thus, the dielectric film formed at a limited temperature cannot have a high dielectric constant, which can be provided if the deposition is performed at higher temperature range.
When a manufacturer stores a variety of types of LSI having different operational frequencies in order to meet customer demand, some types of LSI will be stored and will not be ordered and some types will be ordered in excess of what is stored, which incurs high prices for some customers and low profits for the manufacturer. On the other hand, when the manufacturer cooperates in designing an LSI with a customer, if the customer wishes to change the design in the operating frequency or to reduce the price after the design is completed, the manufacturer and the customer will both suffer from delay of delivery and increased cost.
The present invention is made to solve the above problems and an object of the present invention is to provide a thin film capacitor as a decoupling capacitor having a lower equivalent series inductance than that of the conventional discrete multilayer ceramic capacitor. An object of the present invention is to provide a semiconductor device, which is capable of being operated at a higher operational frequency range, capable of being mounted in a reduced area, and capable of being manufactured at a reduced cost and with a reduced delivery time.
According to the first aspect, a semiconductor device comprises: a plurality of elements formed on a semiconductor substrate; an interlayer insulating film covering the plurality of elements; a plurality of wiring blocks including a power source wire block and a ground wire block connected to the plurality of elements; an uppermost insulating film which covers these wiring blocks; and a thin film capacitor formed on the uppermost insulating film; wherein the thin film capacitor comprises at least one set of: a lower electrode, which is electrically connected to either one of the power source wire block and the ground wire block through a contact passing through the uppermost insulating film; an upper electrode, connected to either one block which is not connected to the lower electrode among the power source wire block and the ground wire block, and at least a portion of the upper electrode extends above the lower electrode; and a dielectric layer which is put between the lower electrode and the upper electrode.
In the present semiconductor device, the power source wire and the ground wire of the integrated circuit portion are connected to respective electrodes of the thin film capacitor through contacts, which pass through the uppermost insulating layer. Thus, the distance between the power source wire and one electrode of the thin film capacitor, or a distance between the ground wire and another electrode of the thin film capacitor is as low as the thickness of the uppermost insulating layer. Accordingly, the distance between the power source wire or the ground wire and both electrodes of the thin film capacitor of the present invention is far lower when compared with the distance of the conventional multilayer ceramic capacitor to the LSI mounted on a printed circuit board. Consequently, in addition to the effect of making the dielectric layer thin, a decoupling capacitor is provided which has a very small equivalent series inductance and very small equivalent series resistance. In addition, since the thin film capacitor which functions as a decoupling capacitor is united with the signal processing portion (LSI) by integrating the thin film capacitor on the LSI, so that any particular area is not required for this capacitor integrated LSI and this thin film capacitor integrated LSI contributes to the size and weight reduction of the electronic devices.
In a semiconductor device, the upper electrode is not disposed above the contact for electrically connecting the lower electrode to any one of the power source wire block or the ground wire block.
If the top surfaces of the contact become not flat, and if the lower electrode surface becomes rough, thus even if the film thickness of the dielectric layer becomes locally thin, it is possible to prevent an increase in the leakage current or the breakdown of the dielectric layer if the upper electrode is not disposed on the locally thin dielectric layer.
The thin film capacitor of the present invention is preferably constituted by one set of the multilayer structure composed of the lower electrode, the dielectric layer, and the upper electrode.
The thin film capacitor of the present invention may be constituted by a plurality of a multilayer structure composed of a lower electrode, a dielectric layer, and an upper electrode. However, the increase in the number of the multilayer structures causes an increase in the equivalent series inductance of the capacitor, and the thin film capacitor comprised of one multilayer structure is preferable.
The materials constituting at least a part of the dielectric layer include compounds expressed by the general chemical formula of ABO3, wherein A is at least one element selected from the group consisting of Ba, Sr, Pb, Ca, La, Li, and K; and B is at least one element selected from the group consisting of Zr, Ti, Ta, Nb, Mg, Mn, Fe, Zn, and W; or compounds expressed by the chemical formula (Bi2O3)(Amxe2x88x921BmO3m+1) (m=1, 2, 3, 4, 5), in which A is at least one element selected from the group consisting of Ba, Sr, Pb, Ca, K, and Bi; and B is at least one element selected from the group consisting of Nb, Ta, Ti, and W, or Ta2O5.
Since these materials exhibit far larger dielectric constants than those of SiO2 or Si3N4, these materials make it possible to increase the storage capacity density and to decrease the size of the thin film capacitor.
A manufacturing method for a semiconductor device comprises at least one set of a multilayer capacitor composed of a lower electrode, a dielectric layer, and an upper electrode on a first semiconductor electrode, comprising the steps of: forming a thin film capacitor, in which at least a part of the lower electrode and the upper electrode is exposed; forming a plurality of elements on a second semiconductor substrate; forming a interlayer insulating film covering those elements; forming on the interlayer insulating film a plurality of wiring blocks including a power source wire block and a ground wire block connected to the plurality of elements; forming a uppermost insulating layer covering the plurality of wiring blocks; forming contacts, which respectively connecting to the power source wire block and the ground wire block, and which pass through the upper most insulating film; forming connecting portions on the uppermost insulating layer corresponding to a region where the contacts are respectively formed; connecting the exposed portion of the lower electrode to one of the contacts and connecting the exposed portion of the upper electrode to the remaining contacts while positioning a surface for forming the thin film capacitor on the first semiconductor substrate and the uppermost insulating layer of the semiconductor device on the second semiconductor substrate so as to face each other; and removing at least a portion of the first semiconductor substrate while leaving the thin film capacitor on the side of the second semiconductor substrate.
According to the manufacturing method for a semiconductor device of the present invention, the thin film capacitor is formed on a first substrate separately from the integrated circuit portion formed on a second substrate, so that dielectric layer of the thin film capacitor can be formed at a high temperature without being affected by the thermally durable temperature of the integrated circuit portion. As a result, the capacitor performance is increased and the size of the thin film capacitor can be reduced.
In a manufacturing method for the above semiconductor device, when forming the thin film capacitor on the first silicon substrate, hydrogen ions are implanted into the first silicon substrate, and when removing at least a portion of the first semiconductor substrate while leaving the thin film capacitor, the first silicon substrate is separated leaving the region wherein hydrogen ions were implanted.
A manufacturing method for a semiconductor device of the present invention comprises the steps of: forming at least one set of a multilayer structure comprising a lower electrode, a dielectric layer, and an upper electrode on a resin film for manufacturing a thin film capacitor, in which at least a part of the lower electrode and the upper electrode is exposed; forming a plurality of elements on a semiconductor substrate; forming an interlayer insulating film for covering the plurality of elements; forming on the interlayer insulating film a plurality of wiring blocks including a power source wire block and a ground wire block connected to the plurality of elements; forming an uppermost insulating layer covering the plurality of wiring blocks; forming contacts, which respectively connecting to the power source wire block and the ground wire block, and which pass through the uppermost insulating film; forming connecting portions on the uppermost insulating layer corresponding to a region where the contacts are respectively formed; connecting the exposed portion of the lower electrode to one of the contacts and connecting the exposed portion of the upper electrode to the remaining contacts while positioning a surface for forming the thin film capacitor on the resin film and the uppermost insulating layer of the semiconductor device on the second semiconductor substrate so as to face each other; and removing at least a portion of the resin film while leaving the thin film capacitor on the side of the semiconductor substrate.
The manufacturing method for a semiconductor device of the present invention is, similar to the above-described method, capable of producing the thin film capacitor on the resin film separately from the integrated circuit portion formed on a silicon substrate, so that high capacitor performance can be obtained. In order to deposit the dielectric film such as SrTiO3 at high temperature, it is preferable for the resin film having a high thermal durability so as to be able to deposit the dielectric film having a higher dielectric constant higher than those of SiO2 or Si3N4. Furthermore, this manufacturing method makes it possible to mass produce the thin film capacitor on inexpensive thin resin films, so that the manufacturing cost of the decoupling capacitor can be markedly reduced.
The other manufacturing method for a semiconductor device, which comprises the steps of forming a general purpose signal-processing portion by forming a plurality of elements on a semiconductor substrate; forming a interlayer insulating film which covers the plurality of elements; forming on the interlayer insulating film a plurality of wiring blocks including a power source wire block and a ground wire block connected to the plurality of elements; forming a uppermost insulating layer covering the plurality of wiring blocks; and forming contacts, which respectively connecting to the power source wire block and the ground wire block, and which pass through the uppermost insulating film; and the manufacturing method further comprises the step of: forming on the uppermost layer a thin film capacitor which is designed so as to conform with the desired operational frequency of the general purpose signal processing portion.
According to the above manufacturing method, the general purpose semiconductor integrated circuits are manufactured and stored beforehand, so that the manufacturing cost of the semiconductor integrated circuit can be reduced and the semiconductor device which has the same operation frequency as that of the customer""s demand can be shipped within a short delivery time.
The thin film capacitor of the present invention, which is formed on the uppermost insulating layer of a semiconductor device comprises a plurality of elements, an interlayer insulating film covering the plurality of elements, a plurality of wiring blocks including a power source wire block and a ground wire block, which are electrically connected to the plurality of elements, and an uppermost insulating layer covering the wiring blocks; wherein, the thin film capacitor is formed by at least a set of a multilayer structure comprising: a lower electrode which is electrically connected to one of the power source wire block or the ground layer block through a contact which passes through the uppermost insulating layer; an upper electrode which is electrically connected to any one of the power source wire block or the ground wire block which is not connected to the lower electrode, and at least a portion of which extends above the lower electrode; and a dielectric layer, which is inserted between the lower electrode and the upper electrode.
The thin film capacitor of the present invention can be connected with the power source wire or the ground wire at a very small distance so that the parasitic inductance and the equivalent series resistance of the thin film capacitor can be reduced drastically in addition to the effect of forming the dielectric material into a thin film.
The above thin film capacitor according to the present invention is preferably sealed by a resin.
The thin film capacitor may be sealed with a sealant of a resin after connecting the thin film capacitor and the integrated circuit formed on the semiconductor substrate. In contrast, the thin film capacitor may be connected with the integrated circuit portion after sealing the lower electrode and the upper electrode with a photosensitive resin except each portion of the lower electrode and the upper electrode.